Fuel tank neck seal arrangement

ABSTRACT

A fuel tank has a neck into which a flange of a level sender unit is to be sealed. A seal gasket surrounds the neck and is received between converging seal surfaces, one on the neck and the other on the flange, and the outside of the neck. A flange nut is provided to clamp the flange to the neck, thus compressing the gasket between the seal surfaces to effect a seal.

TECHNICAL FIELD OF THE INVENTION

[0001] This invention relates to a fuel tank neck seal arrangement inwhich a gasket is used to provide a seal effective to seal a fuel tankagainst the escape of gasoline molecules from the tank.

BACKGROUND OF THE INVENTION

[0002] Many new vehicles feature the use of blow-moulded plastic fueltanks for a variety of reasons. The primary reason is often to maximisethe volume of fuel that a vehicle may carry. The plastic tank enablesthis by virtue of the fact that it may be moulded into shapes that steeltanks may not be capable of, therefore effectively increasing thestorage capacity of the same vehicle when compared to a steel tank.

[0003] However, simple plastic fuel tanks bring with them otherproblems, primarily to do with emissions as molecules of gasoline areable to percolate through the polymeric structure of the material usedfor blow moulded fuel tanks (eg: high density polyethylene—HDPE).

[0004] Fuel tank manufacturers have developed methods of minimising thispercolation process. One method is to convert the inside skin of thetank by a chemical process called fluorination and another method is to‘co-extrude’ another material with the HDPE such that a barrier is setup rather like an onion skin inside the main material of the tank wall(this barrier layer being a type of nylon).

[0005] Once emissions from the main tank structure have been minimised,there still remains the problem of minimising emissions from theelastomeric seals that are used on some of the connections to the tank.One of the seals is that used on the so-called ‘level sender flange’.

[0006] This flange is used to close an aperture in the fuel tank wherethe fuel level sender and the vehicle's electric fuel pump are assembledinto the fuel tank.

[0007] Many configurations of gasket have been seen in use to seal thisopening, and many have deficiencies associated with, for example:manufacturing, product assembly and cost.

[0008]FIGS. 1 and 2 show a typical flange-to-tank neck sealingarrangement such as found in many existing European vehicles. A tankneck 10 with an external thread 12, a level sender edge flange 14 and aflange retaining nut 16. A gasket 18 is fitted between the neck 10 andthe flange 14. The gasket has a significant influence on the variabilityof the nut tightening torque and applied load during assembly, and alsoinfluences the ease with which the assembly may be serviced.

SUMMARY OF THE INVENTION

[0009] The proposed solution identifies a simple gasket arrangement thatutilises a minimum of material, a low cost material, an improved initialassembly condition and an improved service condition. The gasket or sealmethod also affords an improvement to vehicle hydrocarbon emissions.

[0010] According to the invention, there is provided a fuel tank neckseal arrangement in which a flange is to be sealed against the neck, thearrangement comprising a seal gasket surrounding the neck and receivedbetween converging seal surfaces, one on the neck and the other on theflange, with separate means being provided to clamp the flange to theneck, thus compressing the gasket between the seal surfaces to effect aseal.

[0011] The seal surface on the neck is preferably moulded integrallywith the tank, and the seal surface on the flange is preferably integralwith the flange. The flange may be of metal or plastic.

[0012] The converging seal surfaces can approach one another at avariety of different angles. Preferably both surfaces converge with eachother at the same angle. Preferably the included angle between thesurfaces is in the range between 5° and 25°. However any angle greaterthan 0° could be used.

[0013] The seal gasket preferably has a D-shaped cross-section, and theflat part of the D-shaped cross-section will then fit against the neckbetween the converging seal surfaces. The seal gasket will beconstrained on three sides but may be unconstrained on a fourth side.

[0014] The seal gasket will be made of an elastomeric material which isimpervious to gasoline molecules. Suitable materials will be well knownto those skilled in the art.

[0015] The flange can be clamped to the neck by a threaded nut whichengages with an external thread on the neck. The external thread on theneck can be below the converging seal surface on the neck, so that thenut covers and protects the seal gasket.

[0016] Additional benefits and advantages of the present invention willbecome apparent to those skilled in the art to which this inventionrelates from the subsequent description of the preferred embodiment andthe appended claims, taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will now be further described, by way of example,with reference to the accompanying drawings, in which

[0018]FIG. 1 shows schematically a motor vehicle fuel tank;

[0019]FIG. 2 is a section through a flange-to-neck joint in a prior artfuel tank;

[0020]FIGS. 3 and 4 show a section through a flange-to-neck joint inaccordance with the invention, in loose and tightened positions; and

[0021]FIG. 5 shows the joint of FIG. 4 in additional detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022]FIGS. 1 and 2 also show a conventional moulded plastics fuel tankwith an irregular shape 20, and a fuel filler neck 22. The tank also hasa level sender unit 24 installed through a neck 26 on the top surface.The sender unit 24 may be combined with fuel flow connections 28, andwill have a socket 30 for connection of electrical cables through whicha fuel level signal can be sent to the driver's instrumentation.

[0023]FIG. 3 shows a section through the neck 26 and a flange 32 of thesender unit 24. A flange nut 34 has an internal thread at 36 whichscrews onto an external thread 38 of the neck 26. An annular seal ring40 surrounds the neck 26 and is received between an upwardly sloping rib42 on the neck, and a downwardly sloping outer portion 44 of the flange32.

[0024] The seal ring 40 is D-shaped in cross-section, and the flatportion of the seal ring circumference lies against the outer wall ofthe neck 26.

[0025] When the flange nut 34 is tightened, (see FIG. 4) the seal ring40 is compressed between the outer wall of the neck 26, the rib 42 andthe flange outer portion 44, to complete a seal between the interior andthe exterior of the tank.

[0026] The seal ring or gasket 40 is in a contained seating when fullycompressed.

[0027] The contained seating is constructed from an outer diameter onthe neck of the fuel tank's sender aperture opening and two inclinedfaces, one face adjoins the outer diameter and the other face isconstructed on the flange used to close the fuel sender opening.

[0028] The ‘D’ section gasket 40 assembles over an outside diameter ofthe fuel tank neck 26 onto which it is a transition fit such that thetank may be reasonably handled during assembly without the seal simplyfalling off.

[0029] The ‘D’ section seal is seated onto a face which forms an angleof somewhat less than 90° with the outside diameter mentioned above.

[0030] The fuel level sender flange 32, which closes the aperture in thefuel tank, also has an angled face, again of somewhat less than 90°, onits underside, where the ‘D’ section seal comes into contact with it.

[0031] When the flange retaining nut 34 is driven down the thread on thefuel tank opening neck, the two angled faces (one on the neck, the otheron the flange) contact the seal and the force vectors generated load theelastomer gasket inward toward the tank neck, deforming the seal to tendto fill the trapezium-shaped containment volume created by the tank neckand the level sender flange.

[0032] Thus, the flange retaining nut, when driven home, abuts acombination of solid features (flange plus tank neck) and the drivetorque required to complete the assembly suffers from far lessvariability than in systems where the elastomeric seal forms a componentof the abutment of the flange nut assembly.

[0033] Also, since the seal is housed in a containment volume ofrelatively precise proportions (when compared to other seals) andcapable of close dimensional control, the seal is compressed by a knownamount which suffers from minimal variability, allowing better choice ofmaterial type and sectional area, also bringing cost advantages.

[0034] Service use is also benefited as any swelling of the seal whichmay take place due to exposure to hydrocarbons is minimised due to thevery small contact available with the hydrocarbon via the mating facegap between the level sender flange and the tank neck upper face. Onceswelling is minimised, no radical change in flange nut torque will beexperienced. This is not the case where the gasket forms a component ofthe abutment of the flange nut assembly.

[0035]FIG. 5 shows the solid abutment area, which also serves to limitliquid fuel exposure to the elastomeric seal, and the load vectors usedto contain the ‘D’ section seal. The regions indicated at 46 representthe sealing surfaces; the arrows 48 represent the load vectors on thegasket; the heavy arrow 50 represents the gasket load onto the tank neck26, and the distance 52 represents the abutment of the flange 32 to thetank neck 26. This abutment prevents overstressing of the gasket.

[0036] This gasket/seal method may contribute to the emissionsperformance of the total vehicle in PZEV (Partial Zero EmissionsVehicle), ZEV (Zero Emissions Vehicle) and LEV (Low Emissions Vehicle)applications.

[0037] Although this disclosure has been aimed at the use of this methodof sealing in conjunction with blow-moulded plastic fuel tanks, themethod could equally well be utilised with steel fuel tanks having atypical ‘cam lock’ method of retention for the fuel level sensor/fuelpump closing flange.

[0038] The foregoing discussion discloses and describes preferredembodiments of the invention. One skilled in the art will readilyrecognize from such discussion, and from the accompanying drawings andclaims, that changes and modifications can be made to the inventionwithout departing from the true spirit and fair scope of the inventionas defined in the following claims. The invention has been described inan illustrative manner, and it is to be understood that the terminologythat has been used is intended to be in the nature of words anddescription rather than of limitation.

I claim:
 1. A fuel tank neck seal arrangement comprising: an annularflange and neck and wherein said flange is to be sealed against theneck; the arrangement comprising an annular seal gasket surrounding saidneck converging seal surfaces on said flange and said neck on oppositesides of said gasket so that converging movement of said flange and saidneck will compress said clamp and the gasket between the flange and theneck, compressing the gasket to effect a seal.
 2. An arrangement asclaimed in claim 1, wherein the seal surface on the neck is mouldedintegrally with the tank.
 3. An arrangement as claimed in claim 1,wherein the seal surface on the flange is integral with the flange. 4.An arrangement as claimed in claim 1, wherein the seal surfaces have anincluded angle of between 5° and 25°.
 5. An arrangement as claimed inclaim 1, wherein the seal gasket has a D-shaped cross-section.
 6. Anarrangement as claimed in claim 5, wherein the flat part of the D-shapedcross-section fits against the neck between the converging flange andneck.
 7. An arrangement as claimed in claim 6, wherein the seal gasketis constrained on three sides and unconstrained on a fourth side.
 8. Anarrangement as claimed in claim 1, wherein a threaded nut engages anexternal thread on the neck to enable the nut to cause the gasket to becompressed.
 9. An arrangement as claimed in claim 8, wherein theexternal thread on the neck is below the converging seal surface on theneck.